Cure of a wide variety of diseases or tissue injuries by specific replacement of damaged or malfunctional tissues by use of totipotent, pluripotent or multipotent stem cells is on the horizon in clinical practice (see, e.g., Fuchs, et al., 2000, Cell, 100:143-156; Weissman et al., 2000, Cell, 100:157-168; Blau, et al., 2001, Cell, 105:829-841). To transmute a somatic cell into the variety of cell types needed for tissue regeneration and reconstruction in vertebrates is a realistic goal. In fact, tissues that were formerly considered incapable of extensive regeneration, such as brain, spinal cord, and cardiac muscle, now appear to be capable of reconstruction functionally, at least to some extent, by stem cell populations. Stem cells derived from the embryo and from adult tissues have been shown to have extensive potentials for self-renewal and differentiation.
Therefore, there is a need to develop methods of identifying or isolating stem cells for tissue reconstruction procedures. Investigation in these areas may lead to realistic approaches in the future for stem cell therapy in a variety of human diseases, tissue injuries, and other clinical problems.